Hydraulic pump or motor



R. w. BRUNDAGE 3,034,446

May 15, 1962 HYDRAULIC PUMP OR MOTOR 2 Sheets-Sheet 1 Filed Sept. 6, 1957 1o 2 2a loo May 15, 1962 R. w. BRUNDAGE 3,034,446

HYDRAULIC PUMP 0R MOTOR Filed sept. e, 1957 2 sheets-sheet 2 88 FIG. 3

le 6 O/5 so /so e4 f e5 se O\ee F G 5 Y INVENTOR.

ROBERT W. BRUNDAGE ATTORNEY United States Patent O 3,034,446 HYDRAULIC PUMP OR MOTGR Robert W. Brundage, Willoughby, Ohio (2869 Wakonda Drive, Belnor, St. Louis 21, M0.) Filed Sept. 6, 1957, Ser. No. 682,501 13 Claims. (Cl. 103-126) This invention pertains to the art of hydraulic pumps or motors and more particularly to a hydraulic pump or motor of the positive displacement type intended for high pressure and high eciency applications.

The invention is particularly applicable to a hydraulic pump of the internal gear type and will be described with particular reference thereto, although it will be appreciated that the invention, or at least portions thereof, is equally applicable to other types of hydraulic pumps or motors. In a pump, high and low pressures correspond to discharge and inlet pressures. lf the invention is to be considered in relation to a motor, such high and low pressures Will then become the inlet and discharge pressures.

Hydraulic pumps of the type to which this invention pertains are normally comprised of a housing, a shaft extending into the housing and rotatably supported therein in suitable bearings. A plurality of members, such as intermeshed, internally-toothed and externally-toothed gears, rotate with the shaft in a bearing surface eccentric to the axis of the shaft to define a plurality of increasing and decreasing volume pumping chambers. Inlet and outlet manifolds communicating with these chambers are formed in the housing.

In such pumps and particularly those having pressures greater than 1,000 pounds per square inch, it has been conventional to form the housing in two or more pieces which are held together by a plurality of nuts and bolts extending through longitudinally extending openings in the housing. Such construction is expensive to manufacture, unduly bulky and requires a large amount of time to assemble and disassemble.

In these high pressure pumps, the high pressure in the chambers is on one side of the shaft only. The mechanical forces created by such pressures are uusymmetrical and must be transmitted through the shaft and its supporting bearings to the housing. Because of the size of the forces, it has heretofore been conventional to support the shaft in either roll or ball bearings of the precision type which are not orly very expensive, but are also relatively bulky.

A further problem with internal gear type pumps has been the tendency of the hydraulic forces in the pump to separate the gear teeth at open mesh resulting in leakage from the high pressure chambers to the low pressure chambers. lf the tolerances of manufacture are closely held, little leakage occurs in a new pump. lf the tolerances are not closely held, or if the bearings or gear teeth should Wear under the high mechanical forces, clearances Will be created at the open mesh and leakage will become excessive.

Normally Where the shaft passes through the Wall of the housing to the outside, a packing must be provided to prevent the flow of the hydraulic uid therethrough. ln certain types of pumps, diculty has been experienced with the hydraulic iluid bleeding past the packing when the iluid is at Zero pressure.

The present invention contemplates a new and improved hydraulic pump or motor, hereinafter generally referred to as a hydraulic device, of the general type described which overcomes all of the above referred to diculties and others, and provides a high ef'iciency, high pressure positive displacement hydraulic pump which is simple in construction, is very economical to "ice manufacture, has a maximum useful life and has high hydraulic -and mechanical efficiency throughout its life.

in accordance with the present invention, a hydraulic device of the general type described is provided wherein the housing consists of two pieces which are screwthreaded into assembled relationship. The eccentric surface is formed on a separate ring member having an outer surface concentric with the axis of rotation and means are provided for relatively locating the eccentric member to the housing piece having the inlet and outlet manifolds formed therein as the housing pieces are screwed together. With such a construction, the through bolts heretofore employedV can be eliminated. The external dimensions of the pump can be substantially reduced and the pump housing can be formed by more economical manufacturing methods, such as the use of the impact extrusion techniques.

Further in accordance with the invention, the shaft supporting bearings are in the form of conventional sleeve bearings with portions of the bearing surfaces being recessed and communicated with the high pressure and other portions communicated with low pressure, the recessed portion being so proportioned in area and so circumferentially positioned that the high pressures therein exerts hydraulic forces on the shaft generally equal and opposite to the hydraulic forces on the shaft created by the high pressures in the pumping chambers. With this arrangement, the shaft in eifect is hydraulically iloated, and relatively cheap bearing members may be employed as distinguished from the roller or ball bearings heretofore employed.

Further in accordance with the invention, the eccentric surface is recessed to provide one portion communi- `cated to the high pressure and another portion communicated to the low pressure with both portions so proportioned and positioned as to create unsymmetrical hydraulic forces on the outer surface of the internallytoothed ring gear which substantially balance the unsymmetrical forces on the inner surface of the ring gear.

Further in accordance with the invention, the ring gear is rotatably supported in a ring member separate from the housing and having an outer surface which is relatively loosely positioned in the housing and means are provided between the housing and ring member to form a fixed pivotvpoint about which the ring member can pivot relative to the housing, such pivot point being so located in relation to `the line of action of external forces on the ring member as to create a turning moment on the ring member which will urge the teeth of the gears at open mesh into slight pressure engagement.

Such external forces may either be created hydraulically or by mechanical means, such as a spring or a combination of both.

Further in accordance with the invention, one end of the gear members issealingly engaged with a wall of the housing and the other end of the gear members is engaged by a sealing disc, the sealing disc having an opposite pressure surface exposed to the high pressures Whereby to create a force equal and opposite to the hydraulic force in the high pressure chambers tending to separate the sealing disc and the gear members.

Still further in accordance with the invention, the sealing disc provides a bearing support for the shaft and the radial force of the shaft on the bearing is transmitted to the housing at a point spaced axially from the mid-line of the bearing in amount such that the twisting moments by such forces will be equal and opposite to the twisting moments of axial forces on the sealing disc.

Pressure actuated sealing means are provided for sealing the shaft Where it passes through the housing. Other sealing means form with this packing a closed chamber and the shaft has a radial passage communicating this l Y f 3,034,446

chamber with a point of low pressure in the pump on the axis of the shaft whereby centrifugal force on the iluidV in the radial passage maintains the chamber under a slight hydraulic pressure to maintain the packing in Viirm seal- Y ing relationship with the shaft. .Y

The principal object of the invention is the provision of a new and improved hydraulic device of the general type described which is economical to manufacture, and which has arhigh mechanical and hydraulic efficiency. y Another object of the invention is the provision of a new and improved housing for a hydraulic device of the general type described adapted to handle high hydraulic vpressure whichmay be manufactured in an economical manner with a minimum of machining operations.

Another object of the invention is the provision of a new and improved housing for hydraulic pumps which maybe comprised of two members screw-threaded together.

Another object of the invention is the provision of a new and improved hydraulic pump of the internal gear type having improved means for maintaining the teeth of `the gears at open mesh in a slight pressure relationship and for taking up Wear. i

Another kobjectrof the invention is the provision of a new and improved hydraulic device, including a rotating shaft member Wherein'the shaft is in eifect hydraulically oated in the pump housing.

Anotherobject of the invention is the provision of a new and improved arrangement for journaling the shaft of'a hydraulic pump having substantial radial forces thereon which includes exposing portions of the shaft to the high pressures whereby to create equal and vopposite radial forces thereon. k

Still another object of the invention is the provision of a new and improved arrangement for maintaining a slight pressure on a packing whereby to prevent bleeding of the packing.

The invention may take physical form in certain parts Y and arrangement of parts preferred embodiments of which will be described in detail in this specification and illustrated in the accompanying drawing which is a part hereof and wherein.

FlGURE l is a cross-sectional view perpendicular to the neutral axis of a hydraulic device illustrating a preferredV embodiment of the present invention.

FIGURE 2 is a cross-sectional viewv of FIGURE l taken partially on theline 2-2 and partially on the line Y Za-Za.

FIGURE 3 is a perspective plan layout of the'reccentric ring.

FIGURE 4 is `a cross-sectional view of FIGURE l, taken approximately on the line 4--4Vthereof. Y

FIGURE 5 is a perspective plan layout of the shaft bearing. Y

FIGURE 6 shows an alternative embodiment of the invention. Y A

Referring now tothe drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only, and not for the purposes of limiting same, the iigures show a pump including a housing 10 internally-toothed gear 18, and supported for rotation in a ring 19 having an `'inner surface 20 eccentric to the outer surface 21.

A'Ihe gear 18V may have one or more teeth than the gear 17, and is mounted for-rotation on an axis 18' eccentric to theax's 15 of ,the'shatt 15'so as .to define a plurality of increasing and decreasing volume chambers 22, 23, separated by what may be termed a neutral axis 24 passing through the points of chamber minimum and maximum volume 25, 26 respectively.

The end wall 13 is in sealing engagement with the sides of the gears 17, 18, and is provided with arcuately extending inlet and discharge manifolds 30, 31, separated by stops 32, and in turn communicating With inlet and outlet ports 33, 34 threaded'to receive pipe lttings, not shown.

rlhe inlet andv outlet manifolds 30, v31 as shown, have aV substantial arcuate extent, and are continuously in communication with the increasing or decreasing volume chambers 22, 23 as the case may be. These manifolds increase slightly in radial width toward the maximuml volume point 26.

A sealing disc 36, -both rotatably supports the shaft 15 and is axially movable relative thereto to bear against the left-hand side of the gears 17, 18, to close this axial end of the chambers 22, 23. The sealing disc 36 'has a cylindrical portion 40 which surrounds the shaft 15 and extends into an opening 41 in the end Wall 12. Pliable sealing means in the form of an O-ring 43 positioned in a groove 44 in the cylindrical portion 40 close' the opening 41. y

A pin 45 extends axially through an opening 47 in the eccentric ring 19 into an opening 46 in the end Wall 13 and a notch 48 in the outer periphery of the sealing disc 36. This pin locates the eccentrifity of the ring 19 with the piece of the housing having the inlet and outlet manifolds therein and is an important part of the present invention. The pin incidentally holds the disc 36 against rotation. A passage 37 in the face of the disc 36 communicates the cavity 14 with the high pressure chamber 23. This high pressure exerts a lforce A against a pressure surface 38 on the sealing disc 36 remote lfrom the gears 17, 18 so as to continuously urge the sealing disc 36 into sealing engagement with the gears.

The size of this force may be controlled by adjusting the area of the pressure surface 38, which Varea may be defined as the difference in the total axially facing area of the disc 36 minus the cross-sectional area of the cylindrical portion 4G.

A helical compression spring 5i) bears between the end wall 12 vand the pressure surface 38 to provide an initial sealing force.

It is to be noted that the force A should be equal to the lforce B in the opposite Vdirection created by lthe high hydraulic pressures in the decreasing volume chambers 23 on the sealing disc 36. In this Way, the force A, which may be termed the sealing force, Vis always equal and opposite to the force B which tends to separate the sealing disc from the gears. The spring 5d increases the force A so as to be just slightly Ygreater than the force B,

It is tok be noted that the force B is radially olset from, while'the force A is on, the axis of rotation which forces tend to create aY turning moment on the sealing disc 36. Reference to this turning moment and its counterbalancing will be made hereinafter.

The hydraulic pressures in the decreasing volume chambers 23 exert an unsymmetrical radial force C and C on the axial center of gears 17, 1S respectively. This force C on the gear 17 is transmitted to the shaft 15 and thence to the housing through both the bearing 16 and the shaft 15 being indicated by the radial force E on the axial center of the bearing surfaces, the force between the sealing disc 36 and the shaft 15 being indicated by the radial force F on the axial center of the bearing surfaces, and the force between the sealing disc 36 and the housing 16 Vbeing indicated by the radial force G.

vwear 'is to be obtained. ln accordance with the present i) invention, however, the shaft is in effect hydraulically oated in the bearing 16 and the sealing disc 36.

Thus the bearing sleeve 16 (see FIGURE 5) has a recess 55 on its inwardly facing surface communicated with the high pressures through a radial opening 56 in the sleeve 16, an annular groove 57 in the end wall 13 and an opening 58 leading to the high pressure Outlet port 34. This high pressure recess 55 is closed in on each axial side by a land 60, and on each circumferential end by lands 63, 64 all of which are in sealing contact with the surface of the shaft 15. The inner surface of the bearing sleeve 16 is also provided with a pair of low pressure recesses 65, 66, separated from each other by a land 67, and from the high pressure recess 55 by means of the lands 63, 64 respectively. The low pressure recesses 65, 66 extend axially the full length of the bearing sleeve 16, and are communicated with the low pressure by means of a radial opening 68 in ythe sleeve 16, a circumferentially extending groove 69 surrounding the sleeve, and a passage 61 to the inlet port 33,

The circumferential width of the recess 55 alone or taken with the lands 63, 64 is preferably less than 180 and the circumferential midpoint is diametrically opposite to the high pressure chamber midpoint. The recess 55 has a radially facing area such that the hydraulic pressure therein exerts a force opposed to the force E and just slightly less than one half such force so that the shaft 15 rubs against the lands 63, 64 with a slight pressure to seal the high pressure in the recess 55 from the low pressure recesses 65, 66.

The shaft 15 is also journaled inside the sealing disc 36 and its shaft facing surface is formed substantially identical to a bearing sleeve 16; thus the bearing surface of the sealing disc 36 has a high pressure recess 70 communicated with the cavity 14 through a radial passage 71, and surrounded on each axial side by lands 72, and on each circumferential side by lands 73, 74. Low pressure recesses 75, 76 are separated by a land 77 and communicate with recesses 65, 66 which are at low pressure, through keyway 8.

The function, location and dimensions of the recesses in the shaft supporting surface of the disc 36 are identical to that of the bearing sleeve 16, and will not be described further herein.

The sealing disc 36 has a. force F exerted thereon by the shaft 15. This force F pushes the sealing disc 36 into engagement with one side of the opening 41 and an equal and opposite force G results. In accordance with the invention, the point of engagement of the sealing disc 36 with the opening 41, that is, the housing 11, is oset axially from the axial center of the bearing surface of the sealing disc 36 away from the gears 17, 1S in an amount such that the turning moment of these forces on the sealing disc 36 is equal and opposite to the turning moment of the forces A and B on the sealing disc 36. The sealing disc is thus in complete force balance and has no tendency to either twist relative to the shaft 15 or relative to the end surfaces of the gears 17, 18. The unbalanced radial force C on the inner surface of the outer ring gear is in accordance with the invention almost totally opposed by an almost equal and opposite unsymmetrical radial force on the outer surface thereof. In accordance with the preferred embodiment of the invention, this is accomplished by providing the inner bearing surface of the sealing ring 19 with a low pressure recess 83 bounded on each axial side by lands 84 and on the circumferential ends by lands 85, 86. The circumferential width of the recess and the lands 85, 86 is preferably equal to or less than 180. The recess 83 may be communicated with the low pressure in any desired manner, but in the preferred embodiment a radial passage 87 extends to the outer surface of the sealing ring 19 to the right or low pressure end of a pliable sealing member in form of an O-ring 88 positioned in a circumferentially extending groove S9 in the outer surface of the eccentric The space to the right of the packing ring 18 is communicated with the inlet port 33 by means of an axially v extending passage 91 formed in the end wall 13.

The bearing surface 20 also has formed therein high pressure recesses 80, 81 of a total 180 circumferentialwidth separated from each other by a land 82 and from the low pressure recess 83 by the lands S5, S6. These recesses 80, 81 extend the full axial length of the surface 20 and thus communicate with the high pressure in the cavity 14. It is to be noted that the high pressure in the cavity 14 holds the eccentric ring member 19 in sealing engagement with the left hand surface of the member 13.

The high pressures in the recesses 80, 81 exert an unsymmetrical radially inward force H on the outer surface of the ring gear 18. The size of this force may be varied by changing the size of the low pressure recess 83 in the course of design or manufacture, and in accordance with the invention, the area of the low pressure recess 83 is so formed that the force H will be slightly greater than .the force C so that the outer surface of the ring gear 18 will be held in sealing engagement with the lands 85, 86 to thus prevent leakage between the high and low pressure areas of the bearing surface 20.

The invention also contemplates an arrangement for urging the ring gear 18 towards the inner gear 17 in a direction so as to oppose the forces of the hydraulic pressures in the high pressure chambers tending to separate the gear teeth at open mesh and hold these teeth in pressure sealing relationship.

It will be noted that the pressures in the recesses 80, 81 exert a radially outward force H on the inner surface of the eccentric ring 19 which force is generally on the radial axial midplane through the high pressure chambers. In accordance with the invention, this force is transmitted to the housing in such a manner as to create a turning moment on the eccentric ring member 19 so as to urge the ring gear 18 ina direction to hold the teeth closed at open mesh. It Will be appreciated that any such force would normally simply tend to rotate the two centers of rotation 15', 18 relative to each other and thus to shift the neutral axis of the pump. The arrangement is such that this rotation cannot occur, or if it does occur, is only to a minor amount.

Thus it will be noted that the eccentric ring 19 has an outer surface 21 which is slightly, but radially spaced from the inner wall of the housing 11 and has a radial projection 92 circumferentially spaced from the axial radial midplaue through the high pressure chambers in a direction opposite to rotation. This projection 92 is held against the inner surface of the housing 11 by the radial force H and forms a pivot point about which the ring 19 can pivot relative to the housing. The pivot point or projection 92 is circumferentially oifset from the radial line of action of force H and results in a turning radial moment on the eccentric ring member 19. This turning moment creates a force on the ring gear 18 which urges the teeth at open mesh into a slight pressure engagement. This pressure need not 4be large. Such force holding the teeth in engagement at open mesh tends to. rotate the center 18 around the center 15 in the direction of rotation. However, in order for this rotation to occur, the eccentric ring 19 must move radially in a direction greater than its eccentricity. The projection 92 prevents this and forms a xed pivot point. Obviously other means for forming a fixed pivot point could be provided such as a pin or the like.

The projection 92 performs a function in conjunction with the pliable O-ring 88 which is not readily apparent. Thus the base of the Oring groove 89 is concentric with the outer surface 21 and does` not have a projection corresponding to the projection 92. Thus the O-ring di- Y ing to hold the projection 92 into engagement with the inner wall of the housing 11.

Further, the eccentricity of the surface 20 is made vslightly less than the eccentricity -of the gear members 1d, 19.' By slightly less is meant about .004 for a normal -eccentn'city of about .053 inch. The O-ring opposite the gear teeth at open mesh is thus slightly compressed, creating a radial force further assisting in holding the gear teeth at open mesh in a slight pressure engagement. lt is to be noted, however, that if the pivot point labove referred'to were eliminated, lthe eect of either of these pressures would be to simply rotate the axesrof rotation of the shaft and internal ring gear relative to each other without creating the desired pressure at open mesh.

' This feature is of value when it is realized that while the force H on the ring member 19 tends to exert a turning moment on this ring member, any actual movement is opposed byfriction between the right hand end of the .ring member yand the left hand end of the cavity 14, such Vfriction resulting from axial forces therebetween due to the hydraulic pressures in the cavity 14 on the opposite axial end of the ring member 19. Thus the O-ring 83 provides an additional force tending to hold the gear teeth at open mesh in pressure engagement which would be supplemented by the turningv moment of the force H.

VFfhe construction of the housing 1% is also believed to be unique and highly advantageous in a high pressure hydraulic pump. Thus it is to be noted that the side walls 11 are integral with thebase 12 and extend beyond the pumping members 17, 1S and are provided with internally-threaded surfaces 160 in threaded engagement with externally-threaded surfaces on the outer surface of the yend wall 13. Y

Thus, the end wall 13 and the portion of the housing 12 are brought together by a relative rotational movement. Vin the embodiment shown, the member 13 is pro- 4which extends from the memberY 13 into the eccentric ring 19.' Such pin as also heretofore pointed out extends into engagement with the sealing disc 36 to prevent it from rotation.

' With such a construction, the left hand portion of the housing may be made by lL'ghly efficient and economical manufacturing methods such as by impact extrusion wherein a slug ofmetal, particularly aluminum, is placed in a mold and a die is advanced rapidly under high pressure towards the metal to form it to the shape shown.

1t Iis to be emphasized that using impact extrusion techniques it is impossible to make a wall thick enough to be axily drilled for bolts. Also, this feature becomes Vimportant with pumps having a pressure rating in excs of 1,000 p.s.i.

With such a method of manufacture, theinner surface of the housing may be made suici'ently accurate and with a suiliciently fine surface, that no other machining operation need be performed thereon other than the formation of the threads 100. In this respect it will be noted that there is la substantial clearance between the surface 21 and the inner Surface of the housing 10 which 'clearance is bridged by the pliable sealing ring 88. Tolerances between these surfaces are relatively ummportant. The projection 92 is the only point on the eccentric ring 19 which engages the housing 10. Any slight errors in the tolerancessimply results in a very slight rotation of the centers 15,', 18 relative to each other. ri'his is not "detrimental except .to very Vslightly shift the neutral axis of the device.

' It will be further noted that with this construction, all

f the surfaces on the member 13 which are at all` critical, mainly the left hand surface of the member 13 relative to the axis or" the opening for the sleeve bearing 16, can be machined in a single operation where tolerances and the proper relationship of surfaces can be easily maintained.

FIGURE 6 shows an alternative embodiment of the invention wherein means are provided for maintaining the packing 94 under a slight hydraulic pressure and means are also provided or'reducing the size of the force H.

Y in FlGURE 6, means are provided for closing od the opening All between the packing 94 and the sealing ring 43 from direct communication with the lower pressure. ln the embodiment shown, this is done by eliminating the key 9 and keyway 3 of the preferred embodiment and forming the gear 17 so as to have a sealing lit with the outer surface of the' shaft 15. A radial hole is drilled from the roots of one Vof the Vteeth of the gear 17 through into the shaft 15 and a pin 1194 extends through this hole to ltey the gear 17' to the shaft l5". The shaft 1S has an axially extending passage 102 communicating with the right hand end thereof and thus with the low pressure. The opposite end of therpassage 162 terminates in a radial passage lill opening onto the outer surface of the shaft. Centrifugal force on the iluids in the passage llill maintain the chamber V41 under a slight hydraulic pressure in excess of the low pressure. Such slight pressure tends to hold the packing 94 in sealing engagement with the shaft and to prevent bleeding during operation as would occur if thechamber 41 were at low pressure. Y

For the purpose of reducing the size of the force H', the IG-ring S8 is positioned in a ring grooveV S9 having an effective plane which may generally be stated to be at an angle other than perpendicular to the axis of rotation. Thus a portion 19S of ring groove 89 on the side of the sealing member opposite the high pressure chambers is spaced away from the pressure end of the ring i9 a greater distance than is a portion 106 which is opposite die low pressure chambers.V rIfhe result is that an unsymmetrical radial hydraulic force is created on the external surface o f the sealing member 19. By properly controllingy the relative spacing and the circumferential positions of the protions of the groove 89"', the size and the radial direction and the force'H may :be readily controlled. Y Y

It is to be noted that the portions and 106 are each located on planes which are perpendicular to the axis of rotation and axially spaced. One diametrical side of the portions 155, 166 are interconnected by portion 1417 while the opposite ,diametrical side is connected by a portion 16S. It is to be noted that the portion E07 is axially offset from the portion 108. The portion lds' is located opposite the point of open mesh of the gear teeth and is offset from the high pressure in the cavity 14 the greaterV amount whereby to additionally create an unsymmetrical radial force inwardly on the eccentric ring 19' and thence to the ring gear 1S so as to urge the teeth at openrmesh into pressure engagement. By controlling the difference in the axial ofset'of these two portions, the amount of pressure on these open gear 'teeth may be readily controlled.

balanced radial force on the eccentric ring member 19 and thus on the ring gear 18.

It will thus be seen that embodiments of the invention have been described which accomplish all of the objects heretofore set forth and others to provide a hydraulic pump which may be manufactured at a minimum cost, which will have a high eihciency, which is simple in construction, which will have a long useful life.

it will be appreciated that modications and alterations will occur to others upon a reading and understanding of this specification, and it is my intention to include all such modifications and alterations insofar as they come within the scope of the present invention. In particular, it will be appreciated that the pump could be designed with a radial discharge other than axial as shown. Further it be appreciated that many of the features described herein are equally applicable to vane type devices, While some of the features described herein are applicable to any type of hydraulic device.

Having thus described my invention, l claim:

l. A hydraulic device comprised of a housing including at least rst and second members, at least said second member having an interior cylindrical surface facing radially inwardly, said first member having inlet and discharge openings therein, a bearing ring having an inwardly facing surface eccentric with said cylindrical surface, said bearing ring being movable circumferentially relative to said second member, the improvement whcih comprises said members having an axially. extending threaded engagement whereby they must be relatively turned on assembly and disassembly, and inter-engaging means between said bearing ring and said rst housing member for preventing relative rotation of said bearing ring relative to said first housing member and thus positioning the eccentricity of said bearing ring relative to said openings during turning assembly of said housing members.

2. A hydraulic device comprised of a housing having an interior cylindrical surface facing radially inwardly, said housing including at least first and second members threadably engaged with the axis of the threads parallel and aligned with the axis of said surface whereby said members must be relatively turned for assembly and disassembly, a bearing ring positioned in and with an outer surface generally concentric with said cylindrical surface and a radially inwardly facing surface eccentric therewith, said bearing ring being movable circumferentially relative to said cylindrical surface, pumping members rotatable within said bearing ring and defining a plurality of increasing and decreasing volume chambers, said rst housing member having inlet and discharge manifolds formed therein and means between said first housing member and said bearing ring for locating and maintaining lthe eccentricity of said bearing ring relative to said first member while said housing members are assembled.

3. A hydraulic device of the general type described, comprising in combination a housing having a generally cylindrical interior surface, a. rotatable shaft, an externally-toothed gear mounted for rotation on said shaft, an internally-toothed ring gear mounted for rotation on an axis eccentric to said shaft and defining with said externally-toothed gear a plurality of increasing and decreasing volume chambers some of which chambers on one side of said shaft are at high hydraulic pressures, the teeth of said gears having an open and a closed mesh, a ring member having an outer surface at least slightly spaced from the inner Surface of said housing and thus radially movable in said housing, said ring members also having an inner surface rotatably supporting said ring gear on said eccentric axis, said high pressures exerting a radially outward force on said gear and said ring member on a line generally through the circumferential center of said high pressure chamber, and means of limited circumferential width and circumferentially spaced from said circumferential center in a direction opposite to rotation for transmitting said force to said housing whereby to create a turning moment on said ring member and urge said gears into pressure engagement at open mesh.

4. The combination of claim 3 wherein said means include a projection of limited circumferential extent on the outer surface of said ring member engageable with the inner surface of said housing.

5. A hydraulic device of the general type described comprising in combination a housing having a generally cylindrical internal surface, a shaft rotatable on the axis of said surface, an externally-toothed gear rotatable with said shaft, an internally-toothed ring gear surrounding said fjrst mentioned gear and rotatable on an axis spaced from said shaft axis and defining therewith a plurality of increasing and decreasing volume chambers, one half of which are at high and the other half of which are at low pressure, said high pressures exerting an unsymmetrical radially outward force on said ring gear, an eccentric ring member having an outer surface generally slightly spaced from the inner surface of said housing whereby said eccentric ring member is radially movable in said housing, said eccentric ring member also having an inner surface eccentric with said outer surface and supporting said ring gear, said eccentric member inner surface having circumferentially spaced portions in sealing engagement with the outer surface of said ring gear and other portions recessed therefrom and defining therewith circumferentially spaced high and 10W pressure recesses, means communicating said high and low pressure recesses each to said high and low pressures respectively, said low pressure recess having au Varcuate extent less than said high pressure recess having an arcuate extent at least equal to 180, said recesses each being symmetrically positioned on the side of said shaft corresponding respectively to the high and low pressure chambers whereby to create a hydraulic force on the outer surface of said ring gear opposite to the hydraulic force of the pressures in the high pressure chambers outwardly on said ring gear, said hydraulic forces in said high pressure recess exerting a radially outward force generally on the circumferential center of said high pressure recess and means of limited circumferential extent transmitting said last mentioned force to said housing, said means being circumferentially spaced from said circumferential center in a direction opposite to the direction of rotation whereby to create a turning moment on said eccentric ring member to exert a force to hold the gear teeth in pressure engagement at open mesh and to prevent relative rotation of the axes of rotation.

6. A hydraulic device comprised of a housing defining a generally cylindrical closed cavity, a shaft extending into said housing coaxial with said cavity, an externally and internally-toothed gear rotatable with said shaft on spaced `axes, means sealing the axial ends of said gears, an eccentric ring member surrounding said internallytoothed gear having an inner surface eccentric to the axis of saidshaft and an outer surface slightly spaced from, but generally coaxial with, the internal surface of said housing whereby said ring member is radially movable in said housing and pliable sealing means between said last mentioned surfaces, whereby said eccentric ring member when it moves radially in said housing will compress said pliable sealing means in the direction of movement.

7. A hydraulic device comprised of a housing defining a closed cavity having a cylindrical outer surface, a shaft extending into said housing coaxial with said cylindrical surface, sealing means between said shaft and said housing, an externally and internally toothed gear rotatable with said shaft on spaced axes, means sealing the axial ends of said gears, said gears defining a plurality of revolving increasing and decreasing Volume chambers some of which are at high hydraulic pressures, an eccentric ring member surrounding said internally-toothed ring gear and having an internal surface eccentric with the axis of rotation and an external surface concentric with Y xedY pivot point acting to prevent rotation assaults and slightly spaced from the innerV cylindrical surface of said housing, said high hydraulic'pressures exerting an uusymmetrically radially outward force on said internally toothed gear and ring member, said eccentric ring externalV surface having a continuous generally circumferential grooveV in its outer surface and pliable sealing means in said groove extending radially therebeyond to be in sealing engagement with the inner surface of said housing, means communicating the high pressure to the interior of said cavity on one axial side of said sealing means, means communicating the opposite side of said sealing means to said low pressure, said groove having a variable axial spacing from the axial end of said eccentric ring member whereby the outwardly facing surface of said eccentric ring member on theaxial side of said sealing means exposed to said high pressure varies in a circumferential direction, the axial spacing kof the ring groove from the axial Vend of the eccentric ring member l being soY proportioned and arranged that the effective center of such area is located on the same radial side of the shaft as and generally -at the circumferential midpoint of the high pressure chambers whereby'to create an unsymmetrical radially inward force on said eccentricV ring member to oppose said radially outward force.

8. The combination of claim 7 wherein said axial spacing of the ring groove'from the axial end of the ring member is so proportioned as to create a small radially inwardly force on said ring member on the line of open mesh of said gears. Y

9. A hydraulic device of the general type described, comprising in combination: a housinghaving an inner surface, a shaft rotatably supported vin said housing, an

I externally-toothed gear mounted for rotation on said shaft, an internally-toothed ring gear mounted for rotation on an axis eccentric to said shaft and defining with said externally-toothed geara plurality of Vincreasing andV in a direction opposite to rotation for transmitting said force to said housing whereby to create a turning moment on said ring member and urge said gear members into pressure engagement at open mesh. Y

'10. A hydraulic device of the'general type described, comprising in combination: a housing having a generally .cylindrical inner surface, a rotatable shaft in said housing, an externally-toothed gear mounted for rotation on said shaft, yan internally-toothed ring gear mounted for rotation on an axis eccentric' to said shaft and defining with said externally-toothed gear a plurality of increas- Y ing and decreasing volume chambers, some of which are Iat high hydraulic pressures, the teeth of said gears having `an open and a closed mesh, Ya ring member having an outer surface spaced from the inner surface of said housingV whereby said ring member is radially movable in said housing, Said ring member also having an inner surface rotatably supporting said ring gear on said eccentric axis, means creating unsymmetricalY radial forces on said ring member on a predetermined line of action and means between said housing and said ring member to provide Ia flxed pivot `point circumferentially spaced from said inline of action such that said unsymmetrical force creates a turning moment on the ring member to urge the Agear teeth into pressure engagement at open mesh, said of said eccentric axes relative to each other. Y Y

11. A hydraulic device of thelgeneral type described, comprising in combination: y a housing having a generally cylindrical inner surface,` a rotatable shaft rotatable supported in said housing, an externally-toothed gear mounted for rotation on said shaft, an internally-toothed ring gear mounted for rotation on an axis eccentric to said shaft a predetermined amount and defining with said externally-toothed gear a plurality of increasing and ldecreasing volume chambers, some of which `are at high hydraulic pressures, the teeth of said gears having an open and a closed mesh, a ring member having an outer surface spaced from the inner surface of said housing and an inner surface rotatably supporting said ring gear on said eccentric axis, pliable sealing'means between said ring member outer surface and said housing inner surface, said ring member and said housing mechanically inter-engaging at a single xed pivot point close to the circumferential midplane of the high pressure chambers, the dimensions of said housing and ring member. on the diametrical line through said point being such as to compress the pliable sealing means diametrically opposed Vfrom such point anV amount greater than adjacent the pivot point, said eccentric surfa having an eccentricity slightly less than the eccentricity of said gears whereby to provide a radial force onA said ring gear to hold the teeth in pressure engagement at open mesh.

12. The combination of claim 1l wherein said ring member has an axially facing surface in frictional engagement with an axially facing surface on said housing, said ring member having Ian opposite axially facing surface, and means exposing said opposite axially facing surface to said hydraulic pressure to hold Said first mentioned axially facing surfaces in frictional engagement.

13. In a positive displacement hydraulic device comprised of in combination: a housing having an interior inwardly facing surface defining a pumping cavity at least portions of which surface are generally cylindrical; a shaft extending into said housing and rotatable on the axis of said cylindrical portion; an externally toothed gear supported on said shaft for rotation therewith; an internally-toothed gear having teeth in sliding, sealing engagement with said externally toothed gear and rotatable about an axis spaced from said shaft axis by a predetermined gear eccentricity determined by said gear teeth; said axes defining the gear neutral axis; a bearing ring having a radially inwardly facing cylindrical surface rotatably supporting said internally toothed gear yand a radially outwardly facing outer surface; said gear teeth moving from points of open to points of closed mesh, both located on the gear neutral axis and as the gears rotate, defining a plurality of revolving pumping chambers; a sealing member in Vsealing engagement with one axial end. of said gear; a manifold member in sealing engagement with the other axialend of said gears and having a pair of arcuate inlet and outlet ports therein opening towards said gears; said manifold member also having a pair Vofllands, one at each arcuate end of said ports and one adjacent each of the closed and open mesh of said gears; said chambers each having an opening which moves past said lands and communicates its respective chamber alternately with said ports; the line of movement width of said lands being slightly greater than `the line of movement width of the openings from said chambers to said ports, high pressure chambers on one radial side of the lands being at high discharge pressure whereby a resultant radially outward force is exerted on said internally toothed gear on the same side of the axisas the high pressure chambers, the improvement which comprises said bearing ring outer surface having a clearance from said housing surface less than said gear eccentricity whereby said ring is radially movable in said housing, said ring outer sur-face having a projection located in a direction from saidradialforce such that said force moves said projection into `engagement with said housing and pivots said ring to exert a closing force on said gear teeth at open mesh.

References Cited in the le of this patent UNITED STATES PATENTS Rotermund Jan. 23, 1923 Hawkins July 3, 1923 Wilsey Feb. 5, 1929 Wilsey July 2, 1929 Wilsey July 2, 1929 Hill Aug. 14, 1934 Pigott Feb. 12, 1935 Nichols Apr. 13, 1937 Wahlmark Oct. 11, 1938 14 Wishart June 17, 1941 Sibley July 28, 1942 Zenner, etal Feb. 1, A1944 Painter July 31, 1945 Shaw July 30, y1946 Potts Mar. 28, 1950 Burt June 17, 1952 Nichols Oct. 3, -1953 Dolan, et al Apr. 9, 1957 Eames May 21, 1957 Adams et al Oct. 15, 1957 Haberland Feb. 18, 1958 FOREIGN PATENTS France Aug. 6, 1956 

